A few days ago, the class was practising phrasal verbs. On one list was log in (or on) and out (or off). The first logs were lengths of wood from trees, and the first logging (not in or on or out or off) was cutting trees down and into lengths. Some time later, sailors measured the speed of a ship by throwing a log off the stern, to which was connected a rope with knots at specified intervals. By counting the number of knots in a specified time, the captain could calculate the speed, then record it (as well as the direction and other relevant information) in a log book. Even the Starship Enterprise has a captain’s log.
Log books came ashore to be used to record any repeated information, including the times of arriving at or leaving work, or starting or finishing a particular task. From there it was a short step to computers, where logging on ensures that only people authorised to use that computer, or any function of it, do so, and records who does what on it, when. All these logs and logging are from Middle English noun logge or lugge.
A student mentioned log tables in maths. These are not related, being tables of logarithms, from Greek logos, word, speech, logical principle and arithmós number (compare arithmetic). A search for log book shows work-related record books, while a search for log table or log table book shows mathematical resources. (The use of logarithms has largely been replaced by calculators and computers.)
[PS 13 Nov: I knew there was another angle. From the 1990s, online diaries etc became known as web logs, weblogs and blogs. There are also vlogs (video-based diaries), which has to one of the ugliest words ever coined.]
So do we log in and out, or on and off? Google Ngrams shows log on and off to be slightly more common than log in and out, but login as a noun has become one word. (Dictionary.com also records logon, but only to define it as login.)
The same student asked about tapping on and off with her Opal card, Sydney’s contactless card for payment of public transport fares. I thought (and I explained to her) that the strike lightly (verb) and a light strike (noun) meanings and the pierce a container to draw liquid from it (verb) and the mechanism to control the flow of liquid (noun) are related, in that you have to tap (strike lightly) on a barrel of water, beer or wine before you can tap (pierce it). But no. The first meaning was the Middle English verb tappen or teppen first, while the second was the Middle English noun tappe/Old English tæppa first. (I haven’t switched the autoreplace on my new computer off yet. It replaced logge with lodge, tappen with happen, teppen with tepee and tappe with tape, but left lugge and tæppa alone.)
Tapping on and off have not reached Dictionary.com. I’m not sure how widespread those verbs are. Certainly they are ubiquitously used in relation to Sydney’s public transport. Melbourne’s public transport website, I have just discovered, talks about touching on and off with its transport card.
English phrasal verbs have many meanings, most of which are not understandable from their component parts. Also, many of them have multiple meanings. One website lists 200, another 390 and a third advertises a book of 1000. The student originally said that we don’t use them very much, and was surprised to find out how common they actually are.
Lesson suggestion: I wrote come, go, bring, take, give, get, put, be and do in one column and up, down, in, out, on, off, away and back in another and challenged the students to find the ones they know, then write or say example sentences and talk about them, or think of possible meanings for other combinations (some of which were actual, less-used ones). (It is also possible to add with in a third column. Note that many more verbs and particles can be used; these are the main ones, to get them started.)
Never Pure and Rarely Simple 