What notions underlie the legal meaning of 'vest' — with its original meanings of 'robe', 'gown'?

How does the legal meaning of ‘vest’ (quoted first below) semantically appertain to its original lay meanings of ‘robe’, ‘gown’ (quoted second)?

the satisfaction of all the requirements necessary for a right to property to
become unconditional; the completion of the transfer of property to a person, so that they can begin to enjoy the rights in that property.

Pearce & Stevens’ Trusts and Equitable Obligations 7 edn 2018, page lxix, Right Column.

vest [17]

Vest was originally used fairly generally for a ‘robe’ or ‘gown’. Its earliest specific application was to a ‘sleeveless jacket worn under an outer coat’. It was Charles II of England who introduced the fashion, and the first reference to vest in this sense is in Samuel Pepy’s diary for 8 October 1666:

‘The King hath yesterday, in Council, declared his resolution for setting a fashion in clothes … It will be a vest, I know not well how; but it is to teach the nobility thrift’. The direct descendant of this is American English vest for ‘waist-coat’.

The British application of the word to an undergarment for the upper part of the body did not emerge until the 19th century. The word came via French veste and Italian veste from Latin vestis ‘clothing, garment’. This went back to the Indo-European base *wes-, which also produced English wear. The derived Latin verb vestīre originally meant ‘clothe’, and hence ‘induct into an office by dressing in the appropriate garments’. It has given English its verb vest [15],
as well as divest [17] and invest. Other English words from the same source include travesty, vestment [13], vestry [14], and vesture [14].

John Ayto, Word Origins (2005 2e), p 522 Right column.

The Meanings of ‘Vest’

It’s right there, hiding in plain sight: the vest in investment. The oldest use of vest in English referred to a “robe” or “gown,” such as those worn in ancient Greece and Rome—logical enough, since the ultimate root of vest is the Latin word vestis (“garment”). The word traveled the Renaissance route from Italian (vesta) to French (veste) to English in the early 1600s. Its modern meaning, “a sleeveless garment for the upper body usually worn over a shirt,” was in use by the late 1600s.

Vest is also a verb in English, but a funny thing happened in the Middle Ages to this Latin-based word: it jumped in meaning from simply “to clothe” to the more bureaucratic definition of “to give (someone) the legal right or power to do something or to own land or property.” This meaning solidifies a metaphorical use of “to vest” in Latin that was closer to “to surround” or “to adorn,” as in: “adorned with the robes of office.” The official robes worn by clergy were the symbols of their positions and, perhaps unsurprisingly, called vestments. Wearing these clothes was a public claim on power, salary, and status.

This is why we sometimes hear the phrase “by the powers vested in me.” The use of vested as an adjective meaning “fully and unconditionally guaranteed as a legal right, benefit, or privilege” (as in “fully vested”) came into the language in the 1700s.

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