etymologeek.com dictionary
English word thereby comes from English by, English there.

Thereby etymology history

Thereby detailed word origin explanation

Dictionary entryLanguageDefinition
by English (eng) Out of the way, subsidiary. (card games) A pass Along a path which runs by the speaker.. Aside, away.. In the vicinity, near.. To or at a place, as a residence or place of business. Indicates an authority, rule, or permission followed.. At some time before (the given time), or before the end of a given time interval.. In the formulae X by X and by Xs, indicates a steady progression, one X [...]
there English (eng) (figuratively) In that matter, relation, etc.; at that point, stage, etc., regarded as a distinct place.. (location) In a place or location (stated, implied or otherwise indicated) at some distance from the speaker (compare here).. (location) To or into that place; thither.. (obsolete) Where, there where, in which place.. In existence or in this world; see pronoun section below. Used to [...]
thereby English (eng) (formal) By it, by that.

Words with the same origin as thereby

Descendants of there
der the'e they