Borum is actually the culmination of many jokes and misunderstandings.
From an early part in the roleplay, user Tahu_of_Fire would accidentally misspell 'Borom' as 'Borum'.
During a period of Jayzor17's inactivity, Caybluk and another Skrall joined Solorok in his visit to New Atero. Unsure of whether to take control of Jayzor's character, Tahu ambiguously referred to this Skrall as "The Skrall that may or may not be Borom."
When Jayzor returned, he ended up taking control over the character. Well, first he made it very clear that this was not Borom, because he was very wound up about that. But then he calmed down and took control over the nameless then-NPC. Deciding that this new character needed a name, he proposed "Borum," thinking it would be a funny reference to both the earlier misspellings and the ambiguity as to the identity of the Skrall. The name became accepted, and Borum an official character.