Return the most frequently occurring word

{=INDEX(cellrange, MODE( MATCH(cellrange, cellrange,0)))}

Built-in Functions

MODE - (MODE.SNGL) The first number that appears the most often in a set.
INDEX - The value from a cell range which is the intersection of a row AND a column.
MATCH - (XMATCH) The position of a value in a list, table or cell range.