Ethernet Label.

Print in pairs and simply either snap or slide them together when it's on the cable.

If you choose the right size then when it's on the cable then it has enough tension to avoid sliding on the cable. If it's not stable enough try the smaller size. Let me know if you need an even smaller or bigger size or anything in between the current two version.

Use a Permanent Pen to write the text to either of the flat sides, or just attach a sticker if you wish or your plate is leaving too much texture marks.
It's working only with PETG, don't even try PLA as it is too rigid and it will break.

Material: PETG
Nozzle: 0.4
Infill: 15%
Prints without support