Salaam ‘Alaykum.
Is it permissible to wear boxers/underwear that have the name of a disbeliever on it, such as Calvin Klein, Tommy Hilfiger, etc.?
Jazaakum-Allaah Khayran.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

There is nothing that requires the prohibition of wearing such brands.

The aforementioned name has become a trademark. Most of those who buy these brands do not even know that they are originally names of people in the first place, let alone assuming that they intend to glorify them.

Moreover, the fact that these clothes are underwear and invisible, then glorifying the name of the owner of the brand is absolutely non-existent in this case!

Nonetheless, if one wants to abstain from wearing such clothes as a way of precaution in order to be on the safe side, then he may do so.

For more benefit on wearing clothes with non-muslim trademarks, please refer to Fataawa 384358 and 344872.

Allah knows best.