The spelling of the word "most topfull" may seem unusual, but it follows the rules of English phonetics. The pronunciation of this compound adjective is /məʊst ˈtɒpfʊl/. The spelling "topfull" is an archaic form of "topped" or "full to the top," which was common in Shakespearean English. The addition of "most" as a modifier makes the phrase mean "very full to the top." While archaic, the word can provide a sense of old-world charm and an elevated tone to your writing.
The term "most topfull" is not a commonly used phrase, and it does not have a specific etymology. However, it can be understood by breaking it down into its constituent parts.
Firstly, "most" is an intensifier or superlative form of "more", indicating a high degree or level. It comes from the Old English word "mǣst", meaning "greatest" or "foremost".
Secondly, "topfull" combines the words "top" and "full". "Top" refers to the highest part or point of something, while "full" means completely filled or containing as much as possible.
Together, "most topfull" could be interpreted as emphasizing the complete fullness or highest degree of something. However, it is worth noting that this phrase is not commonly used in modern English.