How did the last name for Felicity came about? Just curious because I am actually a Smoak and it isn’t common.

Felicity Smoak is the name of a very minor comic-book character (who is completely different from Arrow's Felicity), so they simply borrowed that name when incorporating Felicity's character into Arrow. In the comics, Felicity Smoak was Ronnie Raymond (Firestorm)'s step-mother.