1640s, "causing bias or prejudice, predisposing the mind to favor," present-participle adjective from prepossess. Opposite meaning "causing agreeable first impression" is attested by 1805.
Entries linking to prepossessing
prepossess v.
1610s, "to get possession of (ground or land) beforehand," from pre- "before" + possess. Meaning "to possess (a person) beforehand with a feeling, notion, etc." is from 1630s; specifically, "to cause (someone) to have a favorable opinion of something, preoccupy the mind or heart of" (1640s). Related: Prepossessed; prepossessing.