I've found evidence that the word scyttel was used in Old English for a boat plug. It is mentioned in the book "Etymological and Pronouncing Dictionary of Difficult Words" by Ebenezer Cobham Brewer, published in 1882:
Old English scyttel, a bolt or bar. A plug in the bottom of a ship.
In the excerpt above, scyttel is given as the Old English form of scuttle which is a current nautical term. OED gives the oldest form of scuttle as skottelle from Middle English and doesn't mention Old English scyttle in the etymology of scuttle; and gives the year 1497 for the first attestation of the original and current nautical sense.
Nautical. A square or rectangular hole or opening in a ship's deck smaller than a hatchway, furnished with a movable cover or lid, used as a means of communication between deck and deck; also a similar hole in the deck or side of a ship for purposes of lighting, ventilation, etc.
A chayne of yron for the skottelles of the haches.
in M. Oppenheim, Naval Accounts & Inventories Henry VII (1896) 323
Oxford English Dictionary, s.v. “scuttle, n.², sense 1.a”, July 2023.
OED says of unknown origin for scuttle but mentions the possible French origin:
The English word is commonly believed to be adopted from the French, and this from the Spanish; but the relation between the three, and the ultimate etymology, remain uncertain. According to a quotation given by Jal, the French word formerly meant the hatch or trapdoor covering the hatchway; if this was the original sense, the word might be a derivative of Dutch or Low German schutten to shut; compare English shuttle (of a dam).
Oxford English Dictionary, s.v. “scuttle, n.², Etymology”, July 2023.
The obsolete word shuttle with the sense "A bolt or bar, as of a door" is from Old English scyttel also; and OED mentions in the etymology that it is ultimately from a prehistoric word with the primitive sense 'to shut'.
Old English scyt(t)el, scyt(t)els < prehistoric *skutil, -isli, < *skut- in scyttan to shut; the two Old English words have different suffixes, but their forms coalesced in Middle English: see -el suffix1, -els suffix. Compare West Frisian skoattel, East Frisian schötel, North Frisian sködel.
The modern dialect shuttle (shittle, shettle, shottle) horizontal bar of a gate (see Eng. Dial. Dict.), is perhaps the same word.
Oxford English Dictionary, s.v. “shuttle, n.², Etymology”, July 2023.