the typical ending of the first element of compounds of Latin words, as -o- is of Greek words, but often used in English with a first element of any origin, if the second element is of Latin origin: cuneiform; Frenchify.
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Word Origin for -i-
from Latin, stem vowel of nouns and adjectives in combination
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012