This is how pH was used for the first time in chemistry. Later, the two letters pH came to be used so that it is easy to type. Acid exists commonly around us. The acetic acid fermentation of microbes produces vineger. Lactic acid fermentation produces yogurt.
Fruits have various organic acids.
Alkali is scarce in everyday life. Burning seaweed produced ashes containing plenty of sodium carbonate. If the river water from a volcano was acid, they poured lime milk, which was a thick mixture of lime and water, to neutralize it. That was about all the alkali that people were able to get. Sodium hydroxide was made possible much later.