Grimm's shift key

In 1786 William Jones noticed that Sanskrit, Greek and Latin were too alike to be chance: they had to share an ancestor. Later, Jacob Grimm (one of the fairy-tale brothers) found that the sounds had shifted in a regular way on the road to the Germanic languages, English among them.

Where Latin has p, English often has f: pater and father, pes and foot. Where Latin has t, English often has th: tres and three. Where Latin has a hard c (said like k), English often has h: centum and hundred.

That is a key you can use. When an English word and a Latin one seem unrelated, try the shift and see if they turn out to be cousins.