Emails being replace to Holiday in the United States?
This has been a bug with Apple mail for a very long time (Funny because the issue just came back to me today). There isn't a clear solution for this issue, but I just go ahead and refer to this thread when I get this issue:

My gmail name comes up as Holidays in the United States

What seems to be the issue is the syncing with Google Calendars. Variations of this bug can be found when your name is changed to one of your contacts.