Pronunciation and etymology of 啱 I was reading the Wikipedia page on hypercorrection, and I noticed this particle section on Cantonese:


  In Cantonese, some speakers omit the initial [ŋ]. For instance, the character 牙 (Jyutping: ngaa4, meaning "tooth"), ends up being pronounced "aa4". Prescriptivists tend to consider these changes as substandard and denounce them for being "lazy sounds" (Chinese: 懶音; Jyutping: laan5 jam1). However, in a case of hypercorrection, some speakers have started pronouncing words that should have a null initial using an initial [ŋ], even though according to historical Chinese phonology, only words with light tones (which correspond to tones 4, 5, and 6 in Jyutping) had voiced initials (which includes [ŋ]). Because of this hypercorrection, words such as 愛 (Jyutping: oi3, meaning "love"), which has a dark tone, are pronounced by speakers with an [ŋ] initial, "ngoi3". 


This lead to me to think about the pronunciation of 啱. Looking at the entry on Wiktionary, it only has one pronunciation (ngaam1). It is in the first tone, but still has an ng- initial, and is the only counter-example I could find to the above paragraph. How accurate is the above paragraph from Wikipedia? If it is accurate, why is it that only tones 4, 5, and 6 that have ng- initials, and why does 啱 not follow that rule? I am also hoping that the etymology of 啱 will help explain this. I am assuming that 啱 is not the "original character", and is a newly invented character due to uncertain origins. The Wiktionary entry does have some speculations, but I also am wondering if other (possibly definitive) theories exist.
So it is a general rule of thumb that any Cantonese syllable with the voiced initial consonants ng-, n-, l-, m- plus tones 1/2/3 is not "Classical", as it violates the defining voicing-based tone split of the four tones that happened in the transition from Middle Chinese to Modern Chinese. 

This means that 啱 is either not derived from Middle Chinese (so from a Tai-Kadai or an Austroasiatic or other non-Sinitic source), or it has gone through a more complex history that means it's only indirectly traceable to a Old or Middle Chinese lexeme (it thus might have a regular Old/Middle Chinese complement, which is often considered its 本字).

In the world of Chinese word etymology, things have very seldom been certain. A lack of good corpus data and earliest attestations for these dialectal characters is a major reason for the current state of affairs. Not much can be said "definitively" at all, though we do know it is not in the Kangxi Dictionary.

The theories on English Wiktionary seem possible, perhaps even reasonable (though unsourced at this point; I have found a source that points to the connection with 諳 deriving from a certain Mr 楊子靜, perhaps through his 廣州話分韻詞林), but that is all that can be said about them really. 

The other colloquial word that comes to mind with ng- with tones 1/2/3 is 奀, although that has a variant with the null initial too.