What is Seth short for?

Because he didn't eat his vegetables as a kid?

In reply to NOHOME :

It's been a long time, but I recall a mention of "the others" unrelated to Adam and Spare Rib. (Which is what Eve is short for)

Polio? 

Seth may just be short for his size 

Sethtopher

It's also the seventh month of the calendar year on Saturn and brings particularly nasty weather to the southern hemisphere. 

NOHOME said:

Seth is a traditionally masculine name with roots in Egyptian, Hebrew, and the Bible. It can mean "put," "anointed," "compensation," or "appointed." In the Bible, Seth was the third son of Adam and Eve — a replacement for Abel after his brother Cain killed him.

thank you......

Because it's only 4 letters

Beer Baron said:

I don't know what Seth is short for, but Luke is short for a storm trooper.

Three groans.

Sethward tentacles. 

Sethesticle

Elizabeth is a compound name; Beth is also a name by itself.