Simplify the following text for a Grade 7 native English-speaking person.
Original: The etymology of the word histogram is uncertain . Sometimes it is said to be derived from the Greek histos ` anything set upright ' ( as the masts of a ship , the bar of a loom , or the vertical bars of a histogram ) ; and gramma ` drawing , record , writing ' .
Simplified: The word histogram is derived from histos and gramma in Greek .