As part of an update of approved abbreviations, my office changed its long-standing ACB (acoustic ceiling board) to ACT (acoustic ceiling tile). Before coming to this office I had always seen ACT, and it took a bit of time to get accustomed to ACB. No one knows where the unusual abbreviation came from, but it is the more logical of the two, as it includes both acoustic ceiling tile and acoustic ceiling panels. Still, it was decided to change from ACB to ACT because it is unusual. I doubt many contractors will ask an architect, "What's ACT?" but it has not been uncommon for contractors, subs, or suppliers to ask us what ACB is.
The change reminded me of a discussion at a CSI technical committee meeting many years ago when we discussed correct terminology for SpecText. It also brought to mind a similar discussion on LinkedIn, which opened with the question, '"Ceiling TILE" or Ceiling "PANEL" -- What's the correct usage?' At the time of the former discussion I thought, as many do, that ceiling tile is 12 inches square, while ceiling panels are 24 by 24, or 24 by 48 inches. That belief lingers on, and appeared in the LinkedIn discussion.