smattering (n.)

early 15c., smateren, intransitive, "talk idly, chatter; talk ignorantly or superficially," a word of uncertain origin, perhaps imitative. Similar words are found in Middle High German smetern "to chatter" and Swedish smattra "to patter, rattle," and compare Danish snaddre "chatter, jabber," Dutch snateren, German schnattern "cackle, chatter, prattle."

Or it might be a special sense of Middle English smateren "to make dirty, defile" (late 14c.). Middle English Compendium compares bismotered "bespattered," smotten "corrupt, debase, defile."

The older sense is obsolete. The meaning "have slight or superficial knowledge of, be a smatterer," is by 1520s. Related: Smattered; smattering.