Pronunciation: [nˌɒt sˈɛldəm] (IPA) 
"Not seldom" is a phrase that means "not often" or "frequently". The IPA phonetic transcription of this word is /nɒt ˈsɛldəm/. The first word "not" is pronounced as /nɒt/ with a short "o" sound. The second word "seldom" is pronounced as /ˈsɛldəm/ with the stress on the first syllable and a short "e" sound. The use of "not seldom" in a sentence adds emphasis to the rarity of an event or occurrence.
"Not seldom" is an idiomatic expression that functions as an adverb and denotes a level of frequency or occurrence somewhere between "sometimes" and "often." It is used to describe an event, action, or situation that takes place with relative frequency but is not considered commonplace or happening on a regular basis.
The phrase can be synonymous with terms such as "frequently" or "occasionally," but it emphasizes the idea that the event being referred to does occur more than the average or expected amount, albeit not to the point of being a common or regular phenomenon.
For instance, if someone says, "He not seldom stays up all night playing video games," it implies that the person in question engages in this behavior more frequently than one might expect or deem appropriate, yet it does not mean that he indulges in it every night.
In summary, "not seldom" conveys the idea of something happening fairly often, but not to the extent that it becomes an everyday occurrence, suggesting a moderate level of frequency. It underpins the notion of unconventional or irregular routines, actions, or events that surpass the norm but still do not qualify as regular or routine.
The etymology of the phrase not seldom can be understood by looking at the origin of its individual words.
1. Not: Not is an adverb that originated from the Old English word naht, meaning nothing. Over time, it evolved to its current form in Middle English.
2. Seldom: Seldom is an adverb that originated from the Old English word seldan, meaning rare or infrequently. Like not, it also went through changes in pronunciation and spelling over time, eventually becoming seldom in Middle English.
When these two words are combined in the phrase not seldom, they create a negation of rarity or infrequency. The phrase is essentially an elevated way of saying not often.
