Knight-Graphable Words

Imagine an arbitrarily large chessboard where some of the squares are labelled with distinct letters of the alphabet. A word is said to be knight-graphable (NG) if there exists some labeling such that a knight can spell out the word by starting on the square labelled with its first letter, then making a valid move to the square labelled with its second letter, and so on until the square labelled with the last letter is reached