Correct spelling for the English word "harth" is [hˈɑːθ], [hˈɑːθ], [h_ˈɑː_θ] (IPA phonetic alphabet).
The word "harth" is of Old English origin. It comes from the Proto-Germanic word "herthō" meaning "burning place" or "fireplace". In Old English, it was spelled "hearth" and referred to the hearthstone or the floor in front of a fireplace where a fire was lit for heating or cooking. Over time, the spelling evolved to "harth", but the meaning remained the same.