CorreptionLeaving aside some extinct meanings correption according to OED is a term used to describe "[s]hortening in grammar" (OED, lemma CORREPTION). The first attested use dates back to the 1871 book The Philology of the English Tongue (London) by the philologist John Earle (1824-1903). On page 539 of said book we read:
"The phenomenon [= smoothing] has sometimes been referred to as 'levelling' (so Jones 1956: §414). But this term usually implies something rather different. I did for a time think of calling it 'correption' (mindful of the Latin grammarians' phrase vocalis ante vocalem corripitur), but have now decided to propose Smoothing as a more generally acceptable term."
In case your mind is not full of Latin grammar rules: Take the Latin verb audīre (to hear) with a long i-vowel. The 2nd person singular present tense subjunctive form is audias with a short i-vowel due to the following vowel which shortens the preceding one. For this shortening process the Latin grammarians used the verb corripere and by substantival derivation correptio.
If truth be told it must be noted that Henry Sweet had decided to propose the term 'smoothing' much earlier, namely in his 1888 book A History of English Sounds from the Earliest Period (Oxford) in §70 on page 22:
Mention is again made by Sweet in his 1891 publication A New English Grammar (Oxford) in §720: