During the act of giving someone fallacio the caregiver gives the receiver a "double" surprise by cupping their balls in one hand while at the same time shoving a finger in his asshole with the other hand.
Last night the blow job my wife was giving me turned into a bi-lonajob when she decided to jiggle my balls and shove her finger in my ass at the same time! That was quite the double surprise.
The wife was feeling frisky last night. She gave me a bi-alonajob and it wasn't even my birthday!