Log logic

Back in the days of wooden sailing ships, a wooden log device on a string was used to measure ship speed.

From this, we have “ship’s log”, being the original  description of the book used to record the speed measurements.

From there, a zigzaggy line via Alan Turing to logging in to a computing device.

But, noting the nautical origins of log, possibly “log on” is more correct than “log in”.

After all, you step onto a ship and into a boat.