APOCOPE [Stress: ‘a-POK-o-py’].
1. The removal of an element at the end of a WORD, usually for informal economy of expression, as in: kit and marge, formed from kitten and margarine. Sometimes a suffix is added to the apocopated form, as in kitty from kitten and AusE journo from journalist. Apocope is common in especially affectionate nicknames: Margery becomes Marge, William becomes Will. Sometimes APHAERESIS and apocope occur together: Elizabeth cut to Liz, detective to tec.

2. The loss of the inflectional endings of Old English, as when singan became sing. See CLIPPING, ELISION.

apocope (gram.) cutting off the end of a word. XVI. — late L. — Gr. apokopé, f. apokóptein cut off.
So apocopate XIX, apocopation XVIII.