The headword phrase is transmitted as a)grou= phgh/, "fountain/spring of the country," in one paroemiographer (Arsenius 1.24b), but the pugh/ version is otherwise standard: see Pausanias the Atticist alpha21; Hesychius alpha837; Photius, Lexicon alpha272 Theodoridis; Appendix Proverbiorum 1.4; Macarius Chrysocephalus 1.3. The phrase itself is taken to come from Old Attic Comedy: Archippus fr. 7 Demianczuk, now 29 Kassel-Austin.
As to its glossing, the Suda's liparw=n (translated here as 'the comfortably-off') is elsewhere the adverb liparw=s, i.e. the first of two adverbs which belong with the phrase as a whole.
Hesychius, citing Sophron, cites an alternative line of exegesis involving birds.