My wife gets cramps in he left calf. wanted to know where do they come from?

Welcome: to the club of all meds nobody knows the exact reason or treatment. make sure there is no reason like low potassium esp. if u take diuretics.

Overuse?: Most likely, her cramping is from overuse from an activity or exercise. If there is also swelling, then consider blood clot (deep vein thrombosis or DVT), though the nature of that pain is usually different from cramping. Peripheral nerve injury like sciatica can cause it too. If persisting or worsening despite local heat and antiinflamatory meds like naproxen, then do get checked. Hope that helps