Likely a modern blend of Gail and Lynn; Gail comes from Abigail, meaning father's joy.
Gaylynne is likely a modern blend of Gail and Lynn, and that makes it a good example of the way English-language names often grow through combination. Gail itself comes from Abigail, meaning father's joy, so even the more modern form keeps a trace of older biblical sentiment.
The double-n spelling gives Gaylynne a slightly more elaborate, personalized look, as if the name were being dressed up for a new generation. The overall effect is friendly, feminine, and distinctly mid-to-late twentieth-century in spirit. Gaylynne belongs to the broad family of names that use familiar syllables to create something new without severing ties to tradition.
It feels polished rather than ornate, and its smooth rhythm makes it easy to imagine in both formal and casual settings. Gaylynne has the comfort of recognition with enough variation to feel individual, which is often exactly why names like this endure.