• 一匹いっぴき — one (animal)
• 何匹なんびき — how many (animals)?
• 匹敵ひってき — to be a match for; to rival
• 数かぞえ方かた：〜匹 — animal counter suffix. ➡️

A pictographic enclosure (匚) marking a measured unit. In old usage, 四丈 of cloth was counted as 一匹. That sense of “a unit” extends to the modern animal counter and to the idea of an equal “match” in 匹敵ひってき.