Webster's Revised Unabridged Dictionary · 1913

Undermeal

Undermeal , noun

[Anglo-Saxon under under + m{not transcribed}l part or portion; compare Anglo-Saxon underm{not transcribed}l midday. See Under, Meal a part, and compare Undern.]

1.
The inferior, or after, part of the day; the afternoon. [Obsolete or Provincial English]
In undermeals and in mornings. — Chaucer
2.
Hence, something occurring or done in the afternoon; esp., an afternoon meal; supper; also, an afternoon nap; a siesta. [Obsolete or Provincial English]
Another great supper, or undermeal, was made ready for them, coming home from ditching and plowing. — Withals (1608)
I think I am furnished with Cattern [Catharine] pears for one undermeal. — B. Jonson
In a narrower limit than the forty years' undermeal of the seven sleepers. — Nash