In the context of communication systems, the latency of a packet indicates the time to delivery (or the round trip time) or in other words, how late the packet is (e.g. it arrives 5ms later than in an ideal system). So I was wondering if the word latency is related to the word late or where it comes from.
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What is the origin of the word "latency"?
According to the Online Etymology Dictionary:
1630s, "condition of being concealed," from latent + -cy. Meaning "delay between stimulus and response" is from 1882; computer sense (latency time) is from 1954.
So: after some stimulus, a signal exists but is hidden or concealed or undetected. After some delay there is a response and the signal is detected.
Is the word latency related to the word late?
No, latency comes from latent, through Latin, from Proto-Indo-European base *la-, "to be hidden".
Late comes through Proto-Germanic, from PIE base *le- "to let go, slacken."
In technical usage, latency = elapsed time (between two events, typically, request-response, generation-detection, etc.). Though it roughly corresponds to the time delay involved, the relation is not so much to 'delay' from the language point of view.
In fact, it is important to note that in technical usage, latency is not even closely related to latent in the sense of hidden, underlying, etc.
Latency as understood in the context of say, data on a hard disk, does not relate to how long the data has been existing undiscovered on the disk platters. A byte of data exists on a storage medium. It cannot be detected without a 'read' mechanism. When a read command is issued, the byte (actually, block of data) is fetched. The time elapsed between the read instruction and the availability of the data for further processing, depends on the characteristics of the storage medium: disk latency. Low latency = fast-response.
It could have been borrowed, though incorrectly, from medical jargon. An infection exists asymptomatically for some period of time called latency. Here it more closely resembles the literary sense of hidden, dormant, etc., like in "someone's latent potential/ talent".