sing someone's praises, to praise someone publicly and enthusiastically: He is always singing his wife's praises.
Origin: 1175–1225; (v.) Middle English preisen < Old French preisier to value, prize < Late Latin pretiāre, derivative of Latin pretiumprice, worth, reward; (noun) Middle English, derivative of the v.; see prize2
early 13c., from O.Fr. preisier "to praise, value," from L.L. preciare, earlier pretiare (c.550; see price). Replaced O.E. lof, hreþ. The noun is attested from early 15c., not common until 16c. Now a verb in most Gmc. languages (Ger. preis, Dan. pris, etc.), but only