ETYMOLOGY
from merry (adj.) + thought (n.)
‘The name alludes to the custom of two persons pulling the furcula of a fowl until it breaks; according to the popular notion, the one who gets the longer (in some districts, the shorter) piece will either be married sooner than the other, or will gain the fulfilment of any wish he may form at the moment.‘
EXAMPLE
“…Fetherstone. O youle make her sicker then.
Greeneshield. I warrant you; would all women thought no more hurt then thou doost now, sweet villaine, Kate, Kate.
Kate. I longd for the merry thought of a phesant.
Greeneshield. She talkes in her sleepe….”
From: North-ward Hoe
By Thomas Dekker & John Webster, 1607
Lexicophilia 