The Collaborative International Dictionary of English v.0.48:

Motherly \Moth"er*ly\, adv.
   In a manner of a mother.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Motherly \Moth"er*ly\, a. [AS. m[=o]dorlic.]
   Of or pertaining to a mother; like, or suitable for, a
   mother; tender; maternal; as, motherly authority, love, or
   care. --Hooker.
   [1913 Webster]

   Syn: Maternal; paternal.

   Usage: Motherly, Maternal. Motherly, being Anglo-Saxon,
          is the most familiar word of the two when both have
          the same meaning. Besides this, maternal is confined
          to the feelings of a mother toward her own children,
          whereas motherly has a secondary sense, denoting a
          care like that of a mother for her offspring. There
          is, perhaps, a growing tendency thus to separate the
          two, confining motherly to the latter signification.
          "They termed her the great mother, for her motherly
          care in cherishing her brethren whilst young." --Sir
          W. Raleigh.
          [1913 Webster]

WordNet (r) 3.0 (2006):

motherly
    adv 1: in a maternal manner; as a mother; "she loved her
           students almost maternally" [syn: maternally,
           motherly]
    adj 1: befitting a mother; warm and nurturing