Etymathology

@DrAliMaths love it! Thank you

OBTUSE. Lat Ob- (against), Tundere (to beat). Literally means 'beaten against'. If you beat against a sharp object it becomes blunt/obtuse

CO-EFFICIENT. Latin Com- (together), Efficiens (producing, productive). The coefficient, 'together' with its variable, gives a 'product'.

REFLEX. From Latin Reflectere (bend back). An angle greater than 180 degrees is one that 'bends back'.

GEOMETRY. From Greek Ge (Earth, land) & Metria (measure). Practical beginnings - a long way from the abstract science it has become.

REGRESSION. Lat Re- (back), Grado (to go, walk, step). The process of 'going back' from the dependent to the independent variable(s)

QUOTIENT. Latin Quotiens (how many times). The quotient is the answer to the question "How many times does … go into …"

DIAGONAL. Greek Dia (through/across), Gonia (Angle) - a line which cuts through a shape from angle to angle.

ISOSCELES. From Greek Isos (equal), Skelos (leg). A shape with equal legs. It is presumably implicit that there must be TWO equal legs?

As seen in Crocodile Dundee (though his was not a rhombus)

PRISM. From Greek Prizein (to saw). Originally referred to a solid wooden figure, literally meaning 'thing sawn'

EQUATION. Lat Aequare 'to make equal'. A statement that 2 quantities are equal is always an equation. Nothing to do with letters or symbols!

@M_rf_C dis- means 'apart'. Dissolvere implies breaking into pieces which go separate ways, while Solvere is a gentler idea of 'loosening'

PARALLEL. From Greek Para (beside), Allellois (each other). If two straight lines are 'beside each other', then they can never intersect.

TRAPEZIUM. Greek Tra- (four), Peza (foot/edge), -ium (diminutive suffix). Literal meaning: little table. Nothing to do with parallel sides!

GRADIENT. Lat Gradior (to walk/step) - originally adj meaning 'going up in equal steps'. Later came to mean the size of the vertical steps