Why “sleveen” is a great word
A person of sly, underhanded cunning and untrustworthiness, from Irish slíbhín (of the same meaning), itself from sliabh ('mountain') + the diminutive suffix -ín, with the implication of an unsophisticated, rustic, and therefore potentially deceitful character. Unlike a 'scoundrel,' who may be openly wicked, or a 'trickster,' who plays for mischief, a sleveen traffics in a more insidious, self-serving deceit. He is the too-eager handshake that leaves your fingers greased, the neighbor whose helpful advice leaves you worse off, the folksy anecdote that is a carefully laid snare—the art of the small betrayal, perfected by those who understand trust is the easiest thing to steal.