gʰedʰ-
“to unite, to join, to fit together”Unite, join, fit
A PIE verbal root meaning "to unite, to join, to seize," continued in Germanic *gadą ("together, united"), whence English together, gather, and good (originally "fitting, suitable"); and *getaną ("to get, to obtain"). The root connects the concepts of joining, fitness, and acquisition.
Discussion
The root *gʰedʰ- ("to unite, to join, to fit") is reconstructed primarily from Germanic evidence: Old English gædere ("together"), gaderian ("to gather"), gōd ("good"), and Old Norse geta ("to get, to obtain"). Latin prehendere ("to seize") has sometimes been compared but the connection is uncertain. Pokorny (IEW 423) discusses the root.
Together (Old English tōgædere, "to-gather, into a union") preserves the root's core meaning of joining or uniting. Gather (Old English gaderian, "to bring together, to unite, to collect") is a direct derivative. The semantic trajectory from "unite" to "collect" is transparent.
Good (Old English gōd, "fitting, suitable, virtuous") derives from the sense of "what fits together, what is proper." The original meaning was closer to "fitting" or "suitable" than to the modern broad sense of moral or qualitative goodness. German gut and Dutch goed are cognates.
Get (from Old Norse geta, reinforcing Old English gietan) originally meant "to obtain, to seize" — what one takes hold of and joins to oneself. The extraordinary versatility of get in modern English (get up, get along, get through, etc.) developed from this concrete sense of obtaining.
Forget (Old English forgietan, "to lose one's hold on, to miss obtaining") uses the prefix for- ("away, astray") with the root: to forget is literally to lose one's grasp on something.
Notes
gsc-gap: source of "get", "together", "good", "gather", "forget"
Laryngeal Analysis
No laryngeal.
Ablaut
Full grade *gʰedʰ-, zero grade *gʰdʰ-.