“Graph” originally abbreviation of graphic formula (OED), from graphic (< Latin graphicus, Greek γραϕικός, < γραϕή drawing or writing. Compare French graphique)
“Diagram” French diagramme, or < Latin diagramma, Greek διάγραμμα that which is marked out by lines, a geometrical figure, written list, register, the gamut or scale in music, < διαγράϕειν to mark out by lines, draw, draw out, write in a register, < δια- through + γράϕειν to write.
“Text”OED: French texte, also Old Northern French tixte, tiste (12th cent. in Godefroy), the Scriptures, etc., < medieval Latin textus the Gospel, written character (Du Cange), Latin textus (u-stem) style, tissue of a literary work (Quintilian), lit. that which is woven, web, texture, < text-, participial stem of texĕre to weave.
“Chapter”OED: Old French chapitre , earlier chapitle < Latin capitulum . diminutive of caput head, used, in ancient Latin, in the senses ‘little head, head of a plant, capital of a column’, and later, those of ‘head-dress of women, chapter of a book, section of a law’….
Ordered Hierarchy of Content Objects (OHCO) model of text