There is an element of Jewish traditional practice and worship called a Tefillin in Hebrew, but in Greek the word used is Phylactery: it is a little box with tiny scrolls of holy acripture worn on key parts of the body. There is an ugly history of anti-Semites being superstitious and weird about this practice in particular, and associating it with the Blood Libel mythos (which is waaaaaaay outside the remit of this forum, Not Great Stuff). The Blood Libel connection is particularly why connecting the evil Wizards who kidnap and ritually murder people to achieve immortality with Phylactery is potentially charged.
Again, not saying anyone really meant much by that along the way...but the 20s are very different than the 70s in terms of people even being able to have this stuff on their radar, and WotC was a bit behind the industry in general in moving away from the term.