oscillo-comb. form
Stress is usually determined by a subsequent element and vowels may be reduced accordingly; see e.g.
oscilloscope n.Origin: A borrowing from Latin, combined with an English element. Etymons: Latin ōscillāre , -o- connective.
Etymology: < classical Latin ōscillāre oscillate v. + -o- connective. Compare French oscillo- (formations in which are found from at least the mid 19th cent.).Formations are found from the late 19th cent. (apparently earliest in oscillograph n.). The third syllable is often reduced to /ə/ in words formed on oscillo-.
This is a new entry (OED Third Edition, September 2004; most recently modified version published online December 2019).