Oneself is the reflexive form of one, used when speaking generally about people. Formal, impersonal, and rather British.
It belongs with the pronoun one, as in one must look after oneself, and it appears in instructions and in writing that avoids naming anybody. It sounds distinctly formal and, to some ears, upper-class, which is why most modern writing uses yourself instead. Style guides mostly prefer you. It is written as one word, and by oneself means alone.
1pronounoneselfThe reflexive form of one, referring to people in general.
“One should not take oneself too seriously.”
Proto-Indo-European
*h₁óynos
Middle English
on
English
one
English, today
oneself
A contracted form of one's self (Mid-16th century). Equivalent to one + -self. one comes from Middle English on. From Middle English oon, on, oan, an, from Old English ān (“one”), from Proto-West Germanic ain, from Proto-Germanic ainaz (“one”), from Proto-Indo-European h₁óynos (“single, one”). a doublet of a and an and Uno. Cognate with Scots ae, ane, wan, yin (“one”); frr ån (“one”); stq aan (“one”); West Frisian ien (“one”); Dutch een, één (“one”); German Low German een; German ein, eins (“one”); Danish en (“one”); Swedish en (“one”); Norwegian Nynorsk ein (“one”), Icelandic einn (“one”); Latin ūnus (“one”) (itc-ola oinos); Russian оди́н, Spanish uno. ഒന്ന്, ஒன்னு, ஒண்ணு, ஒன்று.
Etymology from Wiktionary, CC BY-SA