[sneak]

Neither Photoshop, Kleenex, nor Google have lost trademark protection.

Additionally, the term Yubikey isn't likely to become synonymous with 2FA in any case. Most people don't know that yubikeys work in several different, independent modes, such as FIDO/U2F 2FA, or CCID smartcard, or Yubico OTP (those long annoying strings your yubikey types when it brushes your thigh or hand).

The CCID smartcard mode requires a pin, which is technically two factor authentication (knowledge of PIN and possession of yubikey), which is an entirely different thing than FIDO/U2F 2FA (which is what most people mean when they talk about using a yubikey for 2FA, not that "yubikey" and "2FA" are interchangeable terms).

This is further complicated by the fact that CCID smartcard mode can be used for ssh (via gpg-agent, with ssh keys inside the yubikey itself), AND, separately, OpenSSH (with other keys) can use a yubikey for U2F.