"gleaning" information from something is basically "to take a richer understanding from something where the information comes to one freely, based on observance"

Meaning - freely available fruits of knowledge can be derived from that which - its basically a pun.

The fact that we lost the meta-knowledge around etymology is a sad thing...

There is a podcast by an etymology guy that has amazing insights to words - but, in my limited experience listening to him, lacks some meta meaning -- in that glean means to to take free fruit, glean means to see deeper info, glean means to harvest deeper info from the free info given, knowledge is thought of as fruit...

I was wrong -- it is known:

>>>glean (v.) Look up glean at Dictionary.com early 14c., "to gather by acquisition, scrape together," especially grains left in the field after harvesting, but the earliest use in English is figurative, from Old French glener "to glean" (14c., Modern French glaner) "to glean," from Late Latin glennare "make a collection," of unknown origin. Perhaps from Gaulish (compare Old Irish do-glinn "he collects, gathers," Celtic glan "clean, pure"). Figurative sense was earlier in English than the literal one of "gather grain left by the reapers" (late 14c.). Related: Gleaned; gleaning.

so.... to collect (information) from....