Is it ensure, insure, or assure?
often before vowels pseud-, word-forming element meaning "false; feigned; erroneous; in appearance only; resembling," from Greek pseudo-, comb. form of pseudes "false, lying; falsely; deceived," or pseudos "falsehood, untruth, a lie," both from pseudein "to deceive, cheat by lies."
Productive in compound formation in ancient Greek (e.g. pseudodidaskalos "false teacher," pseudokyon "a sham cynic," pseudologia "a false speech," pseudoparthenos "pretended virgin"), it began to be used with native words in Middle English.
pseudo- or pseud-
False; deceptive; sham: pseudohematuria.
Apparently similar: pseudomyxoma.