Question

Can you have two apostrophes on one word? For example, is it OK to write y'all's?

Answer 1

Yes: a word with multiple contractions can have multiple apostrophes, which is commonly used when writing dialogue.

Explanation:

It's possible to have one word with multiple apostrophes. While it isn't recommended to use this form when writing something like an essay, when writing dialogue for a character, it can be helpful.

Some examples:
"I shouldn't've done this."
"We couldn't've been there."

The example given, "y'all's", is a bit unusual, but wouldn't be out of place in character dialogue and can be used correctly as such.