When H. A. Hellyer is out walking with his family, strangers sometimes approach him and declare, “Allahu akbar!”

Many Westerners may find it hard to believe these days, but Mr. Hellyer does not recoil in fear.

“I’ll be walking out with my kids,” he said, “and someone will say: ‘Oh, they’re so cute. Allahu akbar.’ And I’ll joke, ‘Thank you — now stop talking to my kids.’”

The Arabic phrase, which means simply “God is great,” has, it sometimes seems, become intertwined with terrorism.

The driver of a truck that mowed down 20 people on a Manhattan bike path on Tuesday was said to have cried out “Allahu akbar” before he was shot by a police officer. The men who carried out the attack on the French newspaper Charlie Hebdo in 2015 shouted it during their onslaught. And the phrase rang through the air as a British soldier was run down near military barracks in 2013 and then hacked to death.