According to most historians Pashtuns were Hindus at the Mahmud of Ghaznavi. In fact Mahmud Ghaznavi masacarred a lot of Pashtuns (like Babur did) and it was never called Pakhtunkahwa by anyone.
This is from original sources by historians of that time (not farishta).
"Muslim historians Ibn Haukal, Utbi and Alberuni are unanimous in the view that uptill the time of Mahmud Ghaznavi i.e. almost four hundred years after the death of the Prophet, most of the Afghans were still non-Muslims. Mahmud Ghaznavi ‘had to fight against the infidel Afghans in the Sulaiman mountains.’ Even 200 years later in the encounter between Mohammad Ghori and Prithviraj in 1192 A.D., according to Farishta, Hindu/Buddhist/Animist/Pagan/Shamanist/Zoroastrian Afghans were fighting on the side of the Rajput Chief. "
Again from Alberuni, Ibn Haukal, Utbi:
“…the Ghilzais learning that the troops of Mahmud were returning to Ghazni in detachments laden with plunder laid wait for them in the mountain passes and succeeded in cutting off several of them They had imagined that winter being at hand operations against them would be delayed till the spring by which time they would be in safety in their haunts in the Ghor mountains northeast of Herat But they reckoned without Mahmud That prince hearing of the insult collected a small body of troops and pushing beyond Kandahar pursued the rebels without intermission The season was January 1010 The severity of the weather denied to the Ghilzais refuge in the mountains They were forced to descend into the plain There Mahmud attacked and slaughtered them Indeed he killed all on whom he could lay his sword A few families only succeeded in escaping into the more habitable recesses of the mountains For the moment for years to come they were utterly crushed .”
Timur Lame rules this area, Arghuns (Mongols) and Moghals ruled this area, so did Sikhs. No one called it ‘Pakhtunkhawa’.