Algorithm
The word "algorithm" itself derives from the 9th century mathematician Muḥammad ibn Mūsā al-Khwārizmī, Latinized "Algoritmi". A partial formalization of what would become the modern concept of algorithm began with attempts to solve the Entscheidungsproblem (decision problem) posed by David Hilbert in 1928. Later formalizations were framed as attempts to define "effective calculability" or "effective method". Those formalizations included the Gödel–Herbrand–Kleene recursive functions of 1930, 1934 and 1935, Alonzo Church's lambda calculus of 1936, Emil Post's Formulation 1 of 1936, and Alan Turing's Turing machines of 1936–37 and 1939.
Aporime
The word is derived from the Greek ', which signifies something very difficult and impracticable, being formed from the privative "α", and ', "passage". When a question was proposed to any of the ancient Greek philosophers, especially of the sect of Academists, if he could not give a solution, his answer was "", q.d. "I do not conceive it; I cannot see through it; I am not able to clear it up."