Meaning

noun the noise of soft mud being walked on

verb walk through mud or mire

verb put (a liquid) into a container or another place by means of a squirting action

originFormed by analogy with crush and possibly smash, both of which have senses as types of compression as well as types of attraction. Possibly first attested in 1999 (see Citations:squish) and then later coined or recoined in 2007 by the user Raisin on the forums of the Asexual Visibility and Education Network as "a milder synonym for the word 'crush'". The term was also used with a similar meaning…

Etymology from Wiktionary, CC BY-SA 3.0