Is it ensure, insure, or assure?
c.1400, from Middle French compression (14c.), from Latin compressionem (nominative compressio) "a pressing together," noun of action from past participle stem of comprimere (see compress (v.)). Related: Compressional. Compressional wave is attested from 1887.
compression com·pres·sion (kəm-prěsh'ən)
The state of being compressed.
See data compression.