Compound of akuifer (“aquifer”) + bebas (“free”), literally “free aquifer”, calque of Japanese 自由地下水(じゆうちかすい) (jiyūchikasui, literally “free underground water”).
akuifer bebas (first-person possessive akuifer bebasku, second-person possessive akuifer bebasmu, third-person possessive akuifer bebasnya)