Lam·mas 
(lăməs)
(lăməs)n.
1.
a. A Christian feast formerly celebrated in England, during which bread from the season's first wheat was consecrated at Mass in thanksgiving for the harvest.
b. A Christian feast formerly celebrated in commemoration of Saint Peter's deliverance from prison.
2. August 1, the day on which these feasts were celebrated.
[Middle English Lammasse, from Old English hlāfmæsse : hlāf, loaf; see LOAF + mæsse, Mass; see MASS.]