intercalation, illegitimate throne, (ghost kanji)
閠 is a ghost kanji with no clear standalone meaning. Its listed senses of intercalation and illegitimate throne are likely errors or misattributions, so its meaning should be treated as uncertain.
閠 is a ghost kanji with no established historical origin. It likely arose as a mistaken variant of 閏, possibly by replacing 王 with 玉.
The gate 門 holds a jewel 玉, but this kanji is a ghost with no real meaning. Think of it as a fake gate hiding a fake jewel.
For ケイ, imagine a gatekeeper named Kay guarding the ghost gate: Kay -> ケイ, but the gate leads nowhere.