aphesis

noun

1. the gradual disappearance of an initial (usually unstressed) vowel or syllable as in `squire' for `esquire'
   Terjemahkan ke Indonesia sumber: wordnet30
2. The loss of a short unaccented vowel at the beginning of a word; -- the result of a phonetic process; as, squire for esquire.
   Terjemahkan ke Indonesia sumber: webster1913