Armpit Phobia
An Armpit Phobia is the same as any other phobia (s). Usually picked up from a bad experience / trauma.
His armpit phobia terrified him, and he did anything not to come into contact with it.
Armpit-o-phobia
Fear of armpit.
No tank top for me, I'm armpitophobiac.
Drop your arms, I suffer from armpit-o-phobia.
Drop your arms, I suffer from armpit-o-phobia.