As others have mentioned, it refers to the gear shift. But it actually has a meaningful origin - many years ago, the gear order was not agreed upon. Many cars had a gear shift that was PNDLR (which I've heard pronounced "pendler"), where reverse was at the end. At the time, it was useful to tell the difference between a PRNDL and a PNDLR shift.
Of course that was all before 1971, when PRNDL was mandated by the US government.
Thinkpads are extremely well documented. For how to repair/replace parts, you need the HMM. Just Google for "Thinkpad t14 Gen 1 HMM" and you should find the official PDF on their site. That will tell you, step by step, how to replace the keyboard.
As for the part itself, you can again check Lenovo's site for all compatible parts (FRUs) and find the item number and details. While I wouldn't recommend buying directly from them due to cost, this should give you the information needed to find it elsewhere. eBay has tons of Thinkpads being sold for parts, and many of these will be parted out. You should have no issues finding what you're looking for.