[seanhunter]

Not my field, but my understanding is it's called the Michelson Interferometer because he designed and built the first version a few years before the famous MM experiment for the purpose of measuring the speed of light. See the diagram on page 3 of his 1881 paper "The relative motion of the Earth and of the luminiferous ether" https://zenodo.org/record/1450060 (note this is before the collab with Morley)

Edit to add: I just noticed a fun thing in the conclusion of that paper "In conclusion, I take this opportunity to thank Mr. A. Graham Bell who has provided the means for carrying out this work..."