Grace couldn't have sex with her boyfriendKenny because of her serious phallaphobia.
Kenny couldn't show his dick to his girlfriend Grace because of her phalllaphobia.
The incorrect use or interpretation of a word pertaining to the male genitalia resulting in the substitution of one with a similar sound (viz. malapropism).
"You seen the size o' that ole boy's dong?" asked Cletus, staring bitterly down at his own withered package.
"I ain't interested in how big a turd Jimbo can lay," replied Larry. His phallapropism was no surprise; he'd always had trouble distinguishing between soft vowel sounds.