the.com/expert
Someone who has made every possible mistake in a very narrow field.
means A person with deep knowledge or skill in a specific subject, earned through training or long experience.
from From Latin expertus, the past participle of experiri, to try or test — so an expert is, literally, someone who has been put through it.
Same rootShares ancestry with experience and experiment.
Niels BohrDefined it as making all mistakes in one field.
Old meaningOnce just meant having tried something firsthand.