In Middle English, aloof was originally a nautical term; the loof (now spelled luff) is the windward side of a ship. Smart sailors wanting to avoid a hazard on the leeward side would give the order, "A loof!" From this command we get the idea of steering clear of something (or someone). 

The earliest known use of the word "aloof" in English, meaning "distant physically or emotionally," was in the mid-1500s, with the Oxford English Dictionary (OED) citing an example from before 1535 in the writings of Thomas More.  In Shakespearean English, "aloof" generally meant "at a distance, especially in feeling of interest," implying a sense of being detached or reserved. 

Examples of aloof in sentences: 
"He stayed aloof from the bickering during the meeting." 
"Other people found her cold and aloof." 
"I consider myself warm and friendly, but I act cool and aloof with other people." 
"He encouraged his writers to remain slightly aloof from the world they were covering." 
"They were courteous, but faintly aloof." 
"He was naturally aloof and kept himself to himself." 
"Dominic had held himself aloof from everyone, wounding them in the process." 
"Tessa's tone was cool and aloof, but Rogers could sense the apprehensive undertone." 
"Ted was an aloof and somewhat austere figure." 

Just the facts:

ALOOF Definition & Meaning - Merriam-Webster