Why does "Northerly" mean both from and towards the North?

Question

In the context of wind direction, Wikipedia explains "northerly" as:

...a northerly wind blows from the north to the south.

But when describing the heading of a person or vehicle you would be going in a northerly direction if you were heading from South to North.

The two conflicting definitions are described here.

adj., adv., n., pl. -lies. adj.

1. moving, directed, or situated toward the north.
2. (esp. of a wind) coming from the north.

I believe the same applies to southerly, easterly, westerly.

How did this apparent contradiction come about? Is there a less-confusing alternative when describing the wind?

Answer 1

Winds are also, and perhaps more commonly, referred to by the name of the direction from which they blow (North wind, East wind and so on). I suspect that this is the original and that the -ly form is a later development.

The reason for this is that it is easier and more accurate to estimate the direction of a wind by facing into it rather than away from it so it made sense to refer to a wind by its apparent origin.

In terms of travel it is, again, more sensible and intuitive to speak of the direction we or our vehicles or vessels face as we travel; so we speak of 'going South', 'sailing West' and so on.

Once these conventions became established all other references to winds and travel directions would have to follow suit, otherwise it would be impossible to discuss either of them without becoming totally confused.