The word marubozu means “bald head” or “shaved head” in Japanese. How is that relevant to trading? Marubozu is a candlestick formation of only a body and no wicks (hence the baldness).
It represents a financial instrument that has traded strongly in one direction and that it opened and closed at the high and low price of that particular session.
An up Maru bozu / “bald head” candle means that buyers kept prices under control from opening to closing whilst a down Maru-bozu candle comes to life when opening price equals the high and closing price equals the low, meaning that sellers managed the price from beginning to end.