Problems involving graphs first appeared in the mathematical folklore as puzzles (e.g. Königsberg bridge problem). Later, graphs appeared in electrical engineering (Kirchhof's Law), chemistry, psychology and economics before becoming a unified field of study.

Just before hitting the guardrail the driver was able to regain control and pull out of the skid.

Lolly, huh? Short for Louise no doubt.

Tie a knot in this rope for me, please.