Q From Sue Mauer and Charles Colenaty: Please explain the etymology of the word understand. How did a compound of under and stand come to mean ‘comprehend’?
A It does look puzzling.
The most common sense of the prefix under- in Old English was just the same as our modern word under — of being below or beneath something (as in underground). Very early in its history, though, it already had several subsidiary figurative senses. One was very much like the Latin prefix sub-, such as something lower or subordinate in type (as in understudy or undersecretary), or something of lesser degree (as in underdeveloped or underweight).
There were several other figurative senses of under-, too, whose meanings are hard to sort out. These appeared in a number of Old English verbs that have now vanished from the language. An example is undersecan, to investigate, from secan, to seek. Another came along rather later, in the Middle English period, and has survived: undertake.
Understand has had our modern sense right from the time it was first recorded, in the ninth century. It seems to have originated in one of these subsidiary senses which is now lost to us. After rather more than 1100 years, it’s very hard to be sure exactly what was in people’s minds.