あいづち responding during conversation

言葉の語源 kotoba no gogen - The origin of words:

あいづち aizuchi [相槌]

Meaning: verbal or non verbal responses of agreement while someone is speaking. (While listening to someone you nod for example)

Example: クレイさんは、「そうですね」と相づちを打ちました。
kurei san wa "sou desu ne" to aizuchi o uchimashita.
Clay-mr-(as for)-"right-is"-(question marker)-responded-hit.
Clay agreed with a nod of "that's right".

Origin: This word comes from the conversation-like pounding when making swords during the Edo period. Sword makers would use a hammer called つち （槌） to pound the molten metal into the right shape. Several people would take turns pounding in a rhythm as if conversing with each other but without words. From this came the meaning of responding to someone non verbally while speaking.