decide, judge, verdict, decision
讞 centers on reaching a formal judgment: deciding a case, delivering a verdict, or making a decision. The meanings all relate to the act of judging or deciding in a legal or authoritative context.
讞 combines 言 (speech) with 獻, which likely contributes the sound and the idea of presenting or offering, suggesting a formal spoken judgment. The exact historical development is uncertain.
The left side is 言 (words), and the right side is 獻, which looks like a complex offering. Imagine a judge speaking words that deliver a formal verdict, like offering a decision in court.
For ゲツ, imagine a judge banging a gavel and saying 'Get's the verdict!' — the sound 'gets' cues ゲツ, and the judge is deciding the case.