Gwillyn \g-willyn, gwi-ll-yn\ as a boy's name is a variant of Guillaume (Old German), and the meaning of Gwillyn is "will helmet, protection".

The baby name Gwillyn sounds like Gaillen, Gillon, Gillen and Gillan. Other similar baby names are Gwilym, Galyn, Garlyn, Garllan, Gwayn, Glyn, Gwinn, Gwin, Keillan, Lewellyn, Quillan and Quillen.