One of the unique behaviours of possoms is when they are afraid of a preditor they go into a self induced state appearing like they are dead. When I was a child my brother and I used this word as a code word meaning pretend to be sleeping when our parents whould come to check on us at night. This word has been passed down to my children and grandchildren over the years
Ted and Zelda are playing cards under the bed with a flshlight. Zelda calls out to her brother "Quick get into bed Dad is coming... possom playhouse"