This might make your mind up - Chanty is a toilet receptacle which in days of old went under the bed.

However, my "bible" A.K.A. Longman's "Guide To English Usage" gives the following explanation.

"A shanty is a crude hut. The similiar word for a sailor's work song is SHANTY, or SHANTEY in British English, but CHANTY, or CHANTEY in American English."

So, ye ken noo!!