Micro-Electrical Scanning Tool (MEST)

Original name for the Schlumberger Formation Microscanner (FMS) tool, in it's earlier 2-pad version. The prototype tool was termed the MicroScanning Tool (MST).

Urban myth: The original name was changed after it was revealed that MST stood for maladie sexual transmissible in French; the 4-letter name was changed after the real meaning of the acronym in German was pointed out. It's a good story anyway.