the.com/judas

means A person who betrays someone under the guise of friendship or trust, especially for personal gain.

from From Judas Iscariot, the disciple who, per the Gospels, identified Jesus to his arrest-party with a kiss — for thirty pieces of silver — making his name a byword for betrayal ever since. The word spread into odd corners of English too: a 'Judas kiss' for any treacherous show of affection, a 'Judas goat' for the trained animal that leads others calmly to slaughter while itself surviving, and even 'Judas hole' for the peephole in a prison door — someone always watching, unseen.