at one time vs singly

at one time

prep
  • formerly 

  • simultaneously, at once. 

singly

adv
  • Honestly; sincerely; simply. 

  • Individually; particularly; severally. 

  • Without partners, companions, or associates; single-handed. 

  • In a single or unaccompanied manner; without a companion. 

How often have the words at one time and singly occurred in a corpus of books? (source: Google Ngram Viewer )