An article by Joe Martinelli about the origins of the Hamrun nickname.
Legend of Tas-sikkina

Many translate this as Cutthroats, but a more literal translation is closer to Knife wielders and this nickname was attached to the people of Hamrun many years ago.
Some say that this came about with the birth of the soccer team Hamrun Spartans since way back then, they were regarded as bullies, thus the nickname seemed appropriate.
However, a more interesting explanation has been handed down from one generation to the next and this one, makes perfect sense and takes us back not only to the creation of Hamrun Spartans but even before Hamrun was ever known by its name.
This throws us back to the last years of the Knights of Malta, therefore prior to 1798. Now one may ask, how does Hamrun or, Casal San Giuseppe as it was formerly known as, figure into the history of the Knights?
There are two reasons why Hamrun was important to the Knights. One was because the Aqueduct the Knights built ran from the Rabat area through Hamrun and onward to Valletta, and two, because the Knights had constructed a lookout fort on the hill known as tas-Samra which very conveniently overlooks Marsa Harbour and thus the Knights were able to watch for invaders and other intruders. To this day the evidence of these structures is very much visible but there are other invisible features connected to the transportation of water from the central part of Malta to its capital city, since underground, there exist a number of cisterns which it is believed, provided water storage for when the island ran into draught periods which invariably happened every hot Summer.
A third and lesser known reason for Hamrunĺ─˘s importance to the Knights was the fact that the Knights had built a series of stores which housed their gunpowder provisions. It is not very clear why they chose an area which lies between Blata l-Bajda and the central part of Hamrun in order to build such storage facilities. One reason would probably be that since Hamrun was a sparsely populated hamlet at the time, such explosive stock would produce minimal damage if something went wrong and the magazines blew up. Another reason would perhaps be that the structures were not be readily identifiable to the enemy had an invasion taken place because they were located in the middle (then) of open fields, probably camouflaged by trees and growth. A third possibility would have been that in the event of invasion and the Knights being besieged behind the Valletta Bastions and likewise in Vittoriosa, the locals who knew where to find provisions, would have been able to fight the invaders from the rear and spring a nasty surprise on them.
Towards the end of the rule of the Knights, and the threat of invasion becoming somewhat diminished (in their own mind), these stores were abandoned and were left empty.
It is also believed that intruders from the South of Sicily often found their way to the Island as were regular traders some of whom preferred to stay. Oddly enough, these empty stores provided much needed shelter for these irregular immigrants. It was spacious, clean, somewhat remote and above all, free. Over the years they grew in number and formed a small community of their own. For their own protection, they remained fairly isolated and had to invent ways to keep some of their traditions and at the same time provide themselves with some entertainment.
One way of celebrating the weekend was to hold a traditional dance where various members of this small community could have some fun bearing in mind that they did not openly join the mainstream in case the authorities discovered their irregular stay in Malta and be shipped out back to Sicily, or worse.
Part of this traditional dance involved the wielding of small stilettos which they wore in their socks, waving them in the air and back to their sheaths, presumably without cutting themselves.
As it turned out this form of entertainment caught the eye of some Hamrun inhabitants and probably to the authorities as well, but since these Sicilians posed no security problem and caused the inhabitants no harm, they were left to cope with their meager existence without hindrance. In fact such a dance was apparently quite a spectacle and although it was supposed to be a secret, soon word spread around the island. It was known that every Saturday evening, the celebration took place. In order to protect them, they were never referred to as the Sicilians in case it became a dare to the authorities who would then be forced to act.
Instead they were referred to as Tas-Sikkina referring to the use of the small knife they used in the dance. People started to talk and often invited others to join them and when asked where they were going, they would say that they are going to (Hamrun) see the knife wielders (tas-Sikkina). Thus, when they said that they were going to see tas-sikkina, they were automatically implying that they were going to Hamrun or Casal San Giuseppe.
The nickname stuck and as the population of Casal San Giuseppe grew and when it eventually became known as Hamrun, it was transferred to the inhabitants of that town even after the disappearance of the Sicilians (probably through assimilation), and lives to this day.
The present Hamrun residents sometimes take offence by being dubbed as Tas-Sikkina since they feel that the nickname has long worn out its usefulness, but it will probably stick forever.

Joe Martinelli