All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
A husband calling his wife as "man" does not constitute Thihaar at all. However, it is not polite for him to call her so.
Therefore, do not take into consideration this Waswaas as it may lead to undesirable consequences. So, do your best to repel it and treat it.
For benefit on how to treat Waswaas, please refer to Fatwa 199253.