Low and Lowdown

Low adjective - Being near the equator.

Lowdown and low are semantically related In some cases you can use "Lowdown" instead an adjective "Low".

Lowdown noun - Information not generally available to the public.

Low and lowdown are semantically related in unpleasant topic. Sometimes you can use "Low" instead an adjective "Lowdown", if it concerns topics such as cheap, poor, despicable, depressed.