What is it called when we follow an acronym with a word already in the acronym? [duplicate]

It's been given the ironic and self-referential label RAS syndrome, where RAS stands for Redundant Acronym Syndrome¹.

From Wikipedia:

RAS syndrome

RAS syndrome (where "RAS" stands for "redundant acronym syndrome", making the phrase "RAS syndrome" humorously self-referential) refers to the use of one or more of the words that make up an acronym or other initialism in conjunction with the abbreviated form, thus in effect repeating one or more words.

Two common examples are "PIN (or VIN) number" (the "N" in PIN and VIN stands for "number") and "ATM machine" (the "M" in ATM stands for "machine"). The term RAS syndrome was coined in 2001 by New Scientist.

The more general term in linguistics is the unsurprising redundancy.

¹ _{Thus RAS syndrome, spelled out, is redundant acronym syndrome syndrome, just as PIN number spelled out is personal identification number number.}