The etymology (yes, that’s what I do) is odd. The primary meaning of nostos, the word that nostimos is derived from, is “return”: it’s the word for Odysseus’ return to Ithaca.
Wheat gives a rich return on investment, so nostos also means the yield of ground grain. Hence the adjective means “abundant”, referring to foodstuff; and from there, “wholesome, succulent, nutritious” by Roman times.
As Liddell–Scott tells you.