1925, probably an agent noun from zip (v.1). The trademark taken out on the name that year applied to a boot with zippers, not to the "lightning fastener" itself, which was so called by 1927.
Entries linking to zipper
zip v.1
"move rapidly," 1852, of echoic origin. Meaning "close with a zipper" is from 1932. Related: Zipped; zipping.
zip v.2
"to close or fasten by means of a zipper," 1932, back-formation from zipper (n.). Related: Zipped; zipping; zipless.