It is a fig tree with only one breva 128533; . I suppose it will come from a monotony error, perhaps a barbarism with a similar meaning.
It means uniformity in intonation. In a single tone. Equality. It can be considered as vulgarism of monotony.
MONOTUNIA Uniformity of tone or intonation . Talk without showing any joy or enthusiasm or discomfort, regret or annoyance2 . Lack of variety, which produces boredom or tiredness.