gobemouche

This word is of French origin and literally translated means, fly swallower. So, a person who keeps their mouth open: a silly or naive person.

roinish

Scabby, despicable. (Obsolete)

But any word meaning scabby must make a comeback!

skybosh

An obsolete word for practical joking or tomfoolery.

nidulation

Nesting or nest making.

put on the dog

Time for a phrase today. If it is not obsolete, it certainly must be obscure.

To put on the dog originated as college slang in the 1860s. It means to make a flashy display, by dress or putting on airs.

tziganologist

Here's an interesting one. Not obsolete, but not used everyday, I imagine. Well, for most anyway. A tziganologist studies Hungarian gypsies.

slubberdegullion

An archaic word for a slovenly person.