"enormous," 1590s, from Gargantua, name of the voracious giant in Rabelais' novels, supposedly from Spanish/Portuguese garganta "gullet, throat," which is from the same imitative root as gargle (v.).
Entries linking to gargantuan
gargle v.
1520s, from French gargouiller "to gurgle, bubble" (14c.), from Old French gargole "throat, waterspout," which is perhaps from garg-, imitative of throat sounds, + *goule, dialect word for "mouth," from Latin gula "throat." Related: Gargled; gargling. The earlier, native, form of the word was Middle English gargarize (early 15c.), from Latin gargarizare, from Greek gargarizein.